Help! 3 yr old driving me mad (long)

DS has always been cheeky but generally a good boy, very loving etc. Only 3 months ago whilst away people commented on how well behaved he was and what a credit to me he was etc. Talk about a kiss of death! Last week we went away to Balamory with family and he turned into child from hell. He did end up poorly with an eczema infection whilst away and had to be seen in hospital but I cant belive that this dramatic change in behaviour is all down to this. He regressed to having his dummy nearly all day - only thing that seemed to stop him whinging and screaming. He has started pushing, screaming very agressively when frustrated or doesnt get his own way. Even started scratching & hitting me in the face whilst out for a meal. I felt like one of those poor parents on the tv programmes who has no control over their child initially.
He is back at nursery now and they say he has been a handful for the last few weeks - pushing & smacking, shouting no and generally being disruptive.
What has happened to him?
Anyone else going through something similar??

I'm finding terrible 3's worse than twos. DD has recently become very cheeky & obstinate. Very few punishments last any length of time so I'm constantly having to come up with new ones. Even a smack is having no effect, and is my last resort after going out into the garden to kick the wall in frustration when she won't do what I want . Most days she's a delightful little girl but at times she's a horrible brat whom I struggle to like, I always thought it was just other peoples children I wasn't fond of (not very maternal till I had one myself, still only really like mine most of the time)
She has taken to lashing out at myself at times. She even told me she didn't love me all the time the other day, which cut me to the core. I've always been her absolute favourite over DH, Gran, Papa etc & normally the one she'll pay attention to so I'm stumped. No-one has usurped me & we've no idea how to deal with it.
Hope you get some answers on here & I'll pay close attention too.

My daughter, now 5, started having tantrums when she was about a year old. I had no idea how to handle it. I tried telling off, shouting, even a smack (which made it worse), bribing, being kind, being hard, being sad, often ended up completely loosing the plot myself and still the tantrums came. I always thought when I saw other kids tantruming it was the parents fault?!?! I tried everything, got really down about it, often cried myself to sleep at night even cried at work about it. One day on the way to nursery/work I had such a fight to get her socks and shoes on she ended up tearing my shirt, buttons flying off everywhere, pulling my hair and screaming like an animal that she hated me. She has hit me, drawn blood by pinching my cheek so hard, wet herself, made herself sick from crying and screaming so much, even done a poo on the floor in her bedroom and has broken several toys by throwing them across the room (when I tried shutting her in) and sworn at me!! Sometimes my husband and I have left her upstairs screaming in her bedroom with the door forced shut so that she couldn't get out and have just sat on the stairs in disbelief. Friends had said, send her to her room etc but when we did, if we didn't keep the door firmly shut she would just come out and go mad or, if forced in her room she would wreck it! We felt absolutlely useless and out of control. Sounds terrible doesn't it? All of this went on (this bad) until she was about 3 years old then it very slowly got better and better (very slowly). Was a huge learning curve for me. Do you know what, now, she is the most loving and caring little girl. Doing really well at school, has lots of friends, goes to play at their houses without me and I am always told how polite she is and well behaved etc etc Skips up to me when I pick her up from school always pleased to see me. I think we eventually got to this stage partly because she has grown out of the tantrums (although still rear their ugly head every now and then) but I finally realised that you really do need to ignore the bad behaviour and praise the good. When I was told this I just thought it was rubbish and it is almost impossible to ignore bad behaviour especially when you are out and people stare and thing you can't cope and your child is running wild but I found with my little girl, if she didn't get any attention for bad behaviour it was short lived. Also, I was quick to lose my temper when she had a tantrum (her behaviour did go on for a good couple of years so I think I was justified to loose it now and then!) but I guess she was in a way mimicking me as well. So, I don't know if any of this helps (hindsight is a wonderful thing) but I do believe that if you really can ignore the bad stuff and go totally OTT on the priase they do work out that positive attention is actually nicer than negative attention. I also found it helped me to know that my child wasn't the only one, and someone always has a worse story than yours. Takes a while but you do get there. I have a 10 month old boy who has just started throwing himself on the floor in temper am determined to go down a different route than before so am already walking away from him when he does this - start how you mean to go on! Any advise on crying it out though? Was going to try it from tonight, new bedtime routine etc and see if I can't stop the nightime waking - twice in night and up at 4.30am for the day I work part time and have to get daughter to/from school etc so am desparate for a good nights sleep - any advise would be really apprecaited